Electrical fuse

Abstract

The present invention relates to an electrical fuse element (1) which comprises at least one fusible conductor (3) and a carrier (2). The object is to provide a fuse element (1) for all known tripping characteristics in a cost-effective production technique for the middle and low-current range. Furthermore, by means of a small outer geometry, the fuse element (1) is to be adaptable to modem methods of insertion. The way in which this object is achieved according to the invention is that the carrier (2) consists of a material of poor thermal conduction, in particular of a glass ceramic.

What is claimed is:  
     
       1. A surface mounted electrical fuse element, comprising 
       a sheet-like substrate including a glass ceramic, the substrate having a top and a bottom surface;  
       at least one fusible conductor;  
       a resistive element acting as a heating element, said at least one fusible conductor and said resistive element being arranged on the top surface of the substrate and in thermal contact with each other, and said at least one fusible conductor and said resistive element forming a series circuit; and  
       wherein when a current flows through the series circuit formed by the at least one fusible conductor and the resistive element, the resistive element heats the at least one fusible conductor such that the fuse element exhibits a slow-acting tripping characteristic.  
     
     
       2. Electrical fuse element according to claim  1 , wherein the resistive element is also designed as a fusible conductor. 
     
     
       3. Electrical fuse element according to claim  2 , wherein the resistive element is designed for a defferent nominal current than the at least one fusible conductor. 
     
     
       4. Electrical fuse element according to claim  1 , wherein a distance between the resistive element and the at least one fusible conductor assumes a minimal value when the resistive element and the at least one fusible conductor are arranged lying one over the other separated by an insulating layer or insulation. 
     
     
       5. Electrical fuse element according to claim  1 , wherein the at least one fusible conductor is formed as a multilayer arrangement. 
     
     
       6. Electrical fuse element according to claim  1 , wherein the at least one fusible conductor has a constriction. 
     
     
       7. Electrical fuse element according to claim  1 , wherein the at least one fusible conductor is a wire. 
     
     
       8. Electrical fuse element according to claim  1 , further comprising a cover above each fusible conductor, said cover includes a low-melting substance covered by a thermally stable substance. 
     
     
       9. Electrical fuse element according to claim  2 , wherein the at least one fusible conductor is formed as a multilayer arrangement. 
     
     
       10. Electrical fuse element according to claim  2 , wherein the at least one fusible conductor has a constriction. 
     
     
       11. Electrical fuse element according to claim  2 , wherein each fusible conductor is covered by a low-melting substance, and the low-melting substance is covered by a thermally stable substance. 
     
     
       12. Electrical fuse element according to claim  1  wherein the resistive element is designed for a higher nominal current than the at least fusible conductor. 
     
     
       13. Electrical fuse element according to claim  9  wherein said multilayer arrangement includes a layer of silver and a covering layer of tin. 
     
     
       14. Electrical fuse element according to claim  11  wherein said low-melting substance is a hot-melt adhesive. 
     
     
       15. Electrical fuse element according to claim  11  wherein said thermally stable substance includes a curing embedding compound or a resin. 
     
     
       16. Electrical fuse element according to claim  5  wherein said multilayer arrangement includes a layer of silver and a covering layer of tin. 
     
     
       17. Electrical fuse element according to claim  8  wherein said low-melting substance is a hot-melt adhesive. 
     
     
       18. Electrical fuse element according to claim  8  wherein said thermally stable substance includes a curing embedding compound or a resin. 
     
     
       19. Electrical fuse element according to claim  1  wherein said substrate consists of glass ceramics. 
     
     
       20. A surface mounted electrical fuse element, comprising 
       a sheet-like substrate consisting of a material having a static thermal resistance that is approximately seven times greater than that of Al 2 O 3  for a thermal impedance, the substrate having a top and a bottom surface;  
       at least one fusible conductor;  
       a resistive element acting as a heating element, said at least one fusible conductor and said resistive element being arranged on the top surface of the substrate and in thermal contact with each other, and said at least one fusible conductor and said resistive element forming a series circuit; and  
       wherein when a current flows through the series circuit formed by the at least one fusible conductor and the resistive element, the resistive element heats the at least one fusible conductor such that the whole fuse element exhibits a slow-acting tripping characteristic.